Update Node to Active LTS version v16 (Gallium)

[domoscargin]

Node.js v14 has been in maintenance mode from 19 October 2021. v16 is the active LTS version.

This in turns updates NPM to v8, meaning our lockfile has changed to lockfileVersion 2

This is an internal change that affects development, testing and deployment.

Closes #2504

[domoscargin]

There are no plans to support M1 with the node-sass compiler. You can switch to the sass compiler instead.

dlmanning/gulp-sass#803 (comment)

[domoscargin]

I got this working locally on an M1 machine by running:

nvm use
npm uninstall node-sass -g && npm cache clean -force && npm install node-sass
nvm use
npm install

It might be worth deleting the node_modules directory first as well.

[36degrees]

I have a new M1 mac so tried switching to this branch immediately after cloning the repo, installing and using 16.14.0 without having installed or run GOV.UK Frontend under v14, and was able to install and start without any issues. So wondering if this is 'only' an issue for users migrating from 14 to 16.

[vanitabarrett]

@36degrees If that's the case, it sounds like documenting the steps you need to take when going from 14-16 would be enough?

[36degrees]

@vanitabarrett Yes, I think so.

[domoscargin]

I've done some more testing to confirm that switching from 14 to 16 is the issue.

In that case, I can add some troubleshooting documentation here: https://github.com/alphagov/govuk-frontend/blob/main/docs/contributing/running-locally.md

### Apple silicon troubleshooting
If you have previously installed `govuk-frontend` locally using Node v14 and below, you may encounter problems with the `node-sass` package when updating to Node v16.

To solve this, delete the `node_modules` folder, then run:

nvm use
npm uninstall node-sass -g && npm cache clean -force && npm install node-sass
npm install

Though this does seem like a pretty temporary problem that affects a small group, so we'd probably want to review it down the line.

@EoinShaughnessy Do you have any thoughts?

[EoinShaughnessy]

@domoscargin Hi!

Yeah, I think adding this content is probably a good idea - should help some users, even if only a few.

Do we have an idea of when this issue will no longer affect users?

Also, what sort of problems might they encounter? Would giving an example help users confirm the issue is to do with using Node v14 or earlier?

[domoscargin]

Do we have an idea of when this issue will no longer affect users?

Also, what sort of problems might they encounter? Would giving an example help users confirm the issue is to do with using Node v14 or earlier?

This would stop affecting users once everybody who's installed govuk-frontend locally on their M1 with Node v14 has successfully moved to Node v16. This only affects devs/contributors, since most users don't need to install this repo locally.

Once this change is in place, anybody who installs locally for the first time should have no problems. Additionally, if we migrate our build process to Dart Sass (#2239), this problem should go away for anybody who installs after that change. So it's probably a small(ish) pool of users, but with a potentially long tail depending on when they update.

The problem is specifically with the node-sass package. Users will get node-sass related errors when trying to run npm install or npm start (alphagov/govuk-design-system#2110 (comment))

[EoinShaughnessy]

@domoscargin Great explanation, thanks!

Content looks really good! Just suggesting a few tweaks*:

### Fixing update errors
If you've previously installed `govuk-frontend` locally using Node v14 or earlier, you may see `node-sass`-related errors when updating to Node v16.

To get rid of these errors, delete the `node_modules` folder from the `node-sass` package, then run:

nvm use
npm uninstall node-sass -g && npm cache clean -force && npm install node-sass
npm install

*These might be based on my misunderstanding stuff - if so, sorry!

[lfdebrux]

1️⃣ 6️⃣ 🎉